A general view of Tesoro's Los Angeles refinery in Los Angeles, California October 10, 2014.
REUTERS/Lucy Nicholson
(Reuters) - U.S. oil output could start to take a hit by late 2015, OPEC said on Monday, suggesting the oil price collapse will take time to impact on the shale oil boom.

In a monthly report, the Organization of the Petroleum Exporting Countries (OPEC) left its forecast for non-OPEC supply this year unchanged, but said output of U.S. tight oil, also known as shale, could be curbed.

"Tight crude producers are aware that typical oil wells in shale plays decline 60 percent annually, and that losses can only be recouped by drilling new wells," OPEC said in the report.

"As drilling subsides due to high costs and a potentially sustained low oil price, a drop in production can be expected to follow, possibly by late 2015."

In the report, OPEC left its forecast for 2015 world oil demand growth unchanged and made virtually no change to its estimate of the demand for its crude this year.